(1) Field of the Invention
The present invention relates to radio frequency transmission, and in particular to the design of circuits for radio frequency transmission.
(2) Description of Related Art
Typically in radio frequency transmission, a digital baseband signal is produced and processed in the digital domain for example including finite impulse response filtering before analog-to-digital conversion. Circuits for performing the processing and digital-to-analog converters (DACs) are usually implemented in an integrated circuit (IC). Usually the transmission circuits and reception circuits are implemented in a common integrated circuit referred to as a transceiver.
In general terms, it is desirable to minimise the size of the ICs used in order to minimise the cost of manufacture. Conversely, the integrated circuit size can only be minimised within the constraint of meeting the desired performance parameters. The present invention is concerned with techniques for so minimising the size of the ICs used, whilst meeting performance parameters.
By way of example, such considerations occur is in a 3G (3rd generation) cellular telephone. Two recent changes within the field of transceiver ICs for 3G cellular telephones are (1) the requirement for HSPA (High Speed Packet Access) compliance, and (2) the change in the partitioning between the baseband and transceiver ICs. Previously all digital baseband functions were carried out in the baseband IC and the interface between it and the transceiver IC was purely analogue. More recent standards require the interface to be digital, working to DigRF or similar standards for high speed serial interfacing. This change in partitioning means that some digital baseband functions are carried out in the transceiver IC. Signal conversion (i.e. digital-to-analog for the transmitter) is also now carried out in the transceiver IC.